Pregnancy Conception Calculator

Estimate your conception date, ovulation window, and peak fertile period

Calculate Based On

Select Date

Average Cycle Length (Days)

Estimated Conception Date

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Fertile Window Start

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Fertile Window End

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Estimated Due Date

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How to Use the Conception Calculator

Select your calculation base (either Estimated Due Date or First Day of Last Menstrual Period).
Enter the corresponding date into the date selector.
If calculating by LMP, adjust your Average Cycle Length (default is 28 days).
Click “Estimate Conception Date” to generate your results.

Calculation Formulas

The calculation relies on standardized gestational timeline algorithms:

Conception Date (from EDD) = Due Date – 266 Days

Conception Date (from LMP) = LMP Date + 14 Days + (Cycle Length – 28 Days)

Fertile Window = Conception Date – 5 Days to Conception Date + 1 Day

Frequently Asked Questions (FAQ)

What is the difference between ovulation and conception?

Ovulation occurs when an egg is released from the ovary and remains viable for fertilization for 12–24 hours. Conception occurs when a sperm successfully fertilizes the egg, typically on the day of ovulation or shortly after.

What is a fertile window?

The fertile window is the timeframe when pregnancy is most likely to occur. It spans roughly 6 days: 5 days prior to ovulation plus ovulation day itself, as sperm can survive up to 5 days inside the female reproductive tract.